With the advent of the Global Positioning System (GPS), and the availability of graphically capable, rugged, relatively low cost computers, accurate navigation information coupled with accurate navigational maps has been made available to mariners. The GPS system, as currently available allows the mariner to locate his or her position to within a few meters, to maintain records of courses sailed, to record the location of obstacles or markers, and to plot courses between points that are input by the user or stored in databases. In particular, the location of channels and buoys at harbors are available in databases that can be used in connection with GPS systems. Alternatively, using these computers a mariner could input his location coordinates as obtained through LORAN, RDF or other coordinate positioning systems and accomplish the same result without the use of the GPS system, although no other system is as consistently accurate. Aspects of this technology have been previously patented or described in the published literature.
U.S. Pat. No. 5,898,680 disclosed a system for providing electronic location-specific data to a user. It described a system for providing digital maps and other data to users at remote locations. The position of the user is determined by a GPS receiver. Based on the position of the user, appropriate maps are downloaded from a satellite broadcasting system. U.S. Pat. No. 5,848,373 disclosed a computer aided map location system. It described a way to correlate data such as GPS location data and a set of printed maps. In “The Coast Guard's Differential GPS Program”, 39 J. Inst. of Navigation (No. 4) p. 345-61 is disclosed a Coast Guard project to provide differential GPS service for Harbor and Harbor Approach areas of the coastal United States, having 8-20 m navigation accuracy.
These systems, although potentially extremely useful, are not designed to aid a specific mariner in a specific sailing vessel, in a particular weather determined situation. In particular, the provision of all this information can be overwhelming when a ship is threatened with severe weather and needs to quickly chart a course and locate an appropriately safe harbor suitable for that specific situation for that particular vessel. These systems typically do not provide the information that would enable an informed decision to be made that takes into account the properties of the harbors, or marinas, close enough to be considered as a shelter, the direction of the oncoming weather and the particular characteristics of the vessel such as its height, to determine whether a particular harbor has height restrictions (bridges, etc.) docking requirements (length and width), overall size limitations (displacement for hauling onto land), and depth below waterline limitations (needed to determine whether a particular harbor is appropriate to even consider as a place of shelter).